The goal of this proposal is to develop the commercial potential of a bioassay to detect and guantitate negative-strand RNA viruses. The basis of this bioassay, which has been prototyped with respiratory syncytial virus, is infection-dependent expression of a reporter gene from an artificial viral genome present within the cytoplasm of transformed cells. Negative-strand RNA viruses include some of the most notorious human pathogens and cause significant worldwide morbidity and mortality due to severe respiratory disease, hemorrhagic fever syndromes, etc. Unfortunately very few therapeutic agents and vaccines are available to control these viruses. Efforts to find new antiviral agents and to develop vaccines will require methods to detect and guantitate infectious virus which are amenable to highthroughput assays. Since all viruses are obligate intracellular microbes, any method to detect infectious virus and to determine the effects of various agents on viral replication must be based on cell culture. Traditional cellculture assays even when combined with immunoassays or nucleic acid-based methods are generally labor intensive and difficult to streamline. Significant advances have been made in identifying the cisacting elements and trans-acting factors involved in replication of many pathogenic negative-strand RNA viruses. The technology on which this proposal is based uses this information to develop cell lines in which the expression of an easily measurable enzyme is dependent on infection with a specific virus. PROPOSED COMMERCIAL APPLICATION: Negative-strand RNA viruses include some of the most important emerging human pathogens. The novel bioassay to detect and quantitate many of these viruses described in this proposal will promote efforts to find new antiviral agents and develop vaccines to control these viruses. Also, if sensitivity and specificty issues are addressed, it has the potential to facilitate diagnosis of these viruses in clinical virology laboratories.